Electronic control system

ABSTRACT

An electronic system for controlling the duration of operation of a plurality of repetitively-activated structures produces a control signal representing the duration of operation of the structures from a plurality of input signals representing the values of the parameters which control the duration of operation. The structures are activated by start pulses. The duration of operation of each structure is controlled by the time necessary to drive a corresponding start pulse through a delay line. This time in turn is controlled by the control signal. A plurality of start pulses, each of which controls the operation of a different structure, can be located at different places in the delay line at the same time. The time necessary for each start pulse to travel through the delay line can vary continuously in response to variations in the parameters which control the desired duration of operation. Various circuits are provided to prevent or ensure activation of the structures under special circumstances.

United States Patent 1 1 1111 3,893,432

Krupp et al. July 8, 1975 ELECTRONIC CONTROL SYSTEM PrimaryExaminerCharles .l. Myhre Assistant ExaminerRonald B. Cox Kr V [75]lnvemors' gg f g 3: of Attorney, Agent, or FzrmAlan H. MacPherson; J.

Ronald Richbourg Calif.

[73] Assignee: Fairchild Camera and Instrument Corporation, MountainView, Calif. [57] ABSTRACT [22} Filed: 30, 1971 An electronic system forcontrolling the duration of operation of a plurality ofrepetitively-activated struc- [21] PP 2132905 tures produces a controlsignal representing the duration of operation of the structures from aplurality of 52 [1.8. (:1 123/32 EA; 235/150.21 input Signalsrepresenting the values of the parameters [51] Int. Cl. F02b 3/00 whichcomm the duration of Operation The Struc- 53 n w f Search 123 32 EA, 139E 32 5; tures are activated by start pulses. The duration of op- 235 150 21 eration of each structure is controlled by the time necessary todrive a corresponding start pulse through a [56] Refere e Ci delay line.This time in turn is controlled by the con- UNITED STATES PATENTS trolsignal. A plurahty of start pulses, each of which controls the operationof a different structure, can be 36l20O9 10/197] Kanllazuka E located atdifferent places in the delay line at the same [23132 time. The timenecessary for each start pulse to travel 3:633:75) 9H9" O'Neil] H 123/32EA through the delay lme can vary continuously in re- 3 92p03 9 972wakamatsu" |23/32 EA sponse to variations in the parameters whichcontrol 3,780,711 12/1973 Lindberg 123/32 EA the esir d duration ofoperation. Various circuits are provided to prevent or ensure activationof the struc- FOREIGN PATENTS OR APPLICATIONS tures under specialcircumstances. 2,004,269 8/1970 Germany 123/32 8 Claims, 18 DrawingFigures so 5 om w H v40 DECODE 120 i i so I lllPUT E COMPUTING moon, '7TOIIIJECTOR om OSClLLATOR MM macros i VALVE .THROTTLE reutl host. mmcomm 6217 DOUBLEIUJECT .xsmo'im 20 FUELSHUTOFF %o't l A0 we, m PROCESSORIGITALDELAF ACUUNTER so 720' E DECODE W PICKUP I PUMP PUMP CONTROL IIOMTEMTFML 8 SHEET a wl ATTOR PMEHTEHJUL 8 m5 SHEET FOP 2- 300 hllll.

ELECTRONIC CONTROL SYSTEM BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to an electronic control system and inparticular to an electronic control system for use with an injectionsystem. The electronic control system described in this specification isparticularly suitable for use with fuel injectors for automobileengines. However, the described system can also be used to control anyrepetitively activated equipment where the time of activation depends onmeasurable variables.

2. Prior Art Numerous control systems have been proposed for fuelinjectors. In general, fuel injection control systems respond toselected input parameters from an engine to determine the amount of fuelto be injected into each cylinder. Typical prior art systems haveseveral disadvantages. Among these are the fact that these systems use alarge number of discrete electronic components and thus often arebulkier than desirable. In addition, these systems usually determine theamount of fuel required by each cylinder by approximate techniques ofinsufficient accuracy to comply with present and projected stringent airpollution standards. Often fuel is not injected into each cylinder atthe optimum time for injection, but rather is injected simultaneouslyinto the manifold sections adjacent groups of cylinders. Other problemsassociated with these systems include a lack of reliability andresponsiveness.

SUMMARY OF THE INVENTION The fuel injection control system of thisinvention automatically adjusts the fuel required for each cylinderaccording to the manifold and atmospheric pressures, inlet airtemperature, cylinder head temperature, fuel temperature, engine speed,battery voltage, throttle setting, and other selected inputs. Amongthese other inputs are signals indicating a wide open throttle or afully closed throttle, and other factors affecting fuel consumption.

According to this invention, an electronic control for a fuel injectionsystem comprises means for sensing the values of a plurality ofparameters which determine the amount of fuel to be placed in eachcylinder and for producing a plurality of input signals representingthese values, means for operating on these input signals to determinethe injection time necessary to inject the required amount of fuel intoeach cylinder, and means responsive to the injection time for producingcontrol signals for controlling the opening and closing of a fuelinjector associated with each cylinder.

In one embodiment, the means for converting the values of the inputparameters into input signals representing the amount of fuel requiredby each cylinder comprises a plurality of amplifier means the gains ofwhich are varied according to the values of the input signals. Theoutput signals from these amplifier means are used to control thefrequency of the output signal from an oscillator-sometimes called acomputing oscillator". Pulses are driven through a delay line at a shiftfrequency determined by the frequency of the output signal from theoscillator. As the frequency of the oscillator output signal increases,the shift frequency of the pulses through the delay line increases andvice versa. The time necessary for pulses to travel through the delayline controls the open time of the fuel injectors.

The oscillator frequency can change continuously in response to changesin the values of input signals. Thus the opening and closing times ofthe injector associated with each cylinder likewise can vary from cycleto cycle. In addition, the time that each fuel injector remains open canvary from injector to injector in response to changes in the oscillatorfrequency.

Means are provided for injecting additional fuel into selected cylindersin response to sudden increases in demand and to cut off all fuel to thecylinders in response to selected decreases in demand.

While the electronic control system of this invention is designed tooperate with an engine wherein each cylinder has an adjacent fuelinjector means which is individually controlled according to the fueldemands of that cylinder, this control system can also be adapted tooperate with an engine using batch injection.

In one embodiment, the invention uses operational amplifiers to generatethe signals which control the period of the output signal from thecomputing oscillator. Usually a transducer is connected in the input orfeedback circuit of an operational amplifier. As the value of theparameter sensed by the transducer changes, the impedance introducedinto the circuit changes, thereby changing the gain of the amplifier. Byinterconnecting selectively-poled diodes in parallel and series with aresistor, for example, between the input lead and the output lead of anoperational amplifier, the output signal from the operational amplifieris made piecewise linear. The input signal voltage at which theoperational amplifier begins to produce a linear output signal can becontrolled by varying the nominal voltage on one of the input leads tothe operational amplifier. By combining a plurality of piecewise linearoutput signals from a corresponding plurality of operational amplifiers,the system can be made to generate control signals tailored to theactual operating characteristics of a selected engine. Thus, forexample, the fuel injection time duration can be matched very accuratelyto the parameters upon which time duration depends.

Input parameters such as temperatures can be converted into outputsignals appropriate for use in this control system by placingthermistors, temperature dependent resistive elements, or any otherelement whose characteristics are appropriately temperature dependent,in the input or feedback circuit of the operational amplifier so thattemperature changes vary the output voltage from the operationalamplifier.

DESCRIPTION OF THE FIGURES FIG. 1 shows in schematic block diagram form,the general arrangement of the functional components of the electroniccontrol system of this invention;

FIG. 2 shows in more detail the computing oscillator 30 shown in FIG. 1;

FIG. 3 shows the circuit used to sense selected tem peratures whichaffect engine performance;

FIG. 4a through 411 show circuits used to detect manifold pressure andother parameters which affect engine performance and graphs useful inexplaining the operation of these circuits;

FIGS. 5a, 5b and 5c illustrate in more detail the circuitry comprisingdigital delay 20 (FIG. I);

FIG. 6 shows the injection decoding and control circuitry shown inblocks 60, 70, 80, 90, and 100 of FIG. 1;

FIG. 7 shows special circuitry designed to provide input signals to thecomputing oscillator 30 (FIG. 1) reflecting changes in fuel demand.

FIG. 8 shows the circuitry for producing a signal indicative of throttleposition; and

FIG. 9 shows the fuel pump control, turn on reset and exhaust gasanalysis circuitry.

DETAILED DESCRIPTION The electronic control system of this inventionwill be described in conjunction with a fuel injection system suitablefor use with an eight cylinder automobile engine. With appropriatechanges, this system can be used with engines containing other numbersof cylinders. It should be recognized that this electronic controlsystem is appropriate for use with any repetitivelyactivated equipmentwhere the time of activation depends upon measurable variables.

FIG. 1 shows a schematic block diagram of the system of this invention.A transducer produces a signal every 90 of rotation of the engines crankshaft. This signal, transmitted to that input lead to processor 10labeled 90 pickup, activates processor 10 to produce a pulse which istransmitted to digital delay 20. This pulse is driven through delay at afrequency determined by the fundamental frequency of a clock signal fromcomputing oscillator 30.

The period of the pulses from oscillator 30 is determined by inputsignals from a variety of sources. The primary inputs used to controlthe frequency of the output signal from computing oscillator 30 aresignals representing the absolute manifold pressure, engine temperature(which can be monitored at a variety of places including the exhaustmanifold, block head, crankcase, cylinders or any other point whichyields a temperature which is representative of the engine temperature)air inlet temperature, fuel temperature, speed of the engine andthrottle position. In addition, battery voltage and a measure of thetorque being delivered by the engine can also be used to influence thefrequency of the signal from computing oscillator 30.

The effect of each input parameter on fuel charge varies. Someparameters have a major effect on the fuel charge, while otherparameters have a very small influence on the fuel charge. Under normaloperating conditions, the fuel charge injected by each injector iscontrolled mainly by the manifold pressure and engine speed. Air, fueland water temperature also influence the fuel required, in decreasingimportance as listed under normal hot running conditions only. Duringwarm-up, water temperature is the most important temperature parameterfollowed by the air and fuel temperatures, respectively.

Transient processor 50 computes input signals for use in controllingoscillator 30 from crankshaft and throttle positions. Separate signalsrepresenting wide open throttle position (WOT), fully closed throttle position (FCT), engine speed, power to the crank motor and shut-offinformation are also processed by processor 50. The computing oscillatorresponds to the signals from processor 50 and to its other input signalsand produces an output signal with a frequency controlled by these andother input signals.

The functional relationships between the required fuel charge and theinput parameters depend upon the particular engine configuration. Muchwork has been done defining these relationships. See for example a bookentitled Aircraft Powerplant Handbook" published in January l949 by theU.S. Department of Commerce where many of these relationships arediscussed.

The output pulses from oscillator 30 drive groups of pulses fromprocessor 10 through digital delay 20. The times for the pulse groups topass through digital delay 20 are inversely proportional to thefrequency of the output signal from oscillator 30.

Two pieces of information are derived by the passage of the pulse groupsthrough digital delay 20. Data decode 100 detects the presence of eachpulse group at the beginning of digital delay 20. In response to this,data decode 100 generates a control signal which is transmitted to A"counter 90. This signal steps counter one digit. Counter 90 is capableof counting up to N, where N is an integer representing the maximumnumber of cylinders in an engine (assumed to be eight of thisexplanation). The change in count in counter 90 results in a signalbeing transmitted to injector decode 80. This signal identifies theparticular cylinder into which fuel is to be injected. Injector decode80 then transmits a signal to open the correct injector. Fuel is theninjected into either the manifold or directly into a cylinder.

When the pulse group traveling through digital delay 20 reaches the endof delay 20, a signal is transmitted to data decode 60. Data decode 60then generates a pulse which is transmitted to 8" counter 70. Counter 70likewise can contain N different numbers. The change in count in counter70 results in a signal being transmitted to injector decode 80. Thissignal terminates the injection of fuel.

A plurality of pulse groups are transmitted in sequence through digitaldelay 20. Each pulse group activates in sequence, data decode and datadecode 60 to start and stop the injection of fuel into the appropriatecylinder. In this manner each injector is controlled in sequence toprovide the proper amount of fuel to its corresponding cylinder.

It should be noted that the time required for pulse groups to travelthrough delay 20 varies depending upon the frequency of the outputsignal from oscillator 30. Thus, this control system responds rapidly tochanges in operating conditions of the engine to correct the amount offuel injected into each cylinder.

COMPUTING OSCILLATOR 30 FIG. 2 shows the circuit comprising oscillator30 (FIG. I). The signals to this circuit include signals (-l-TEMP andTEMP) representing selected temperatures and a signal representing themanifold pressure. In general, the fuel required by each cylinderincreases as air temperature, water temperature and fuel temperaturedecrease and as manifold pressure increases. Thus the period of thesignal produced by oscillator 30 (FIG. 2) must increase as thesetemperatures decrease. As the period of oscillator 30 increases, thetime necessary for pulses to travel through delay 20, and thus theinjection time, increases.

Composite signals representing the influence of selected temperaturesare input to oscillator 30 through resistors 30] and 302. A positivesignal proportional to temperature (the +TEMP signal) is transmittedthrough resistor 301. An inverted signal (the TEMP signal) istransmitted through resistor 302. These two signals are generated in amanner to be described later in conjunction with FIG. 3. M08 transistors303, 304, 305 and 306 are connected together to form a switchingcircuit. The sources of transistors 303 and 304 are grounded. The gatesof transistors 303 and 306 are connected together while the gates oftransistors 304 and 305 are also connected together. The gates oftransistors 304 and 305 are connected by lead 318a to the collector oftransistor 318. The gates of MOS transistors 303 and306 are connected bylead 317a to the collector of transistor 317.

The operation of the oscillator circuit will be explained assuming thatinitially transistor 318 is shut off and transistor 317 is conducting.Thus the collector voltage of transistor 318 is the negative voltage ofvoltage source 312 while the collector voltage of transistor 317 is thevoltage of source 312 plus the voltage drop across resistor 322 or aboutzero volts. Accordingly, a negative voltage approximately equal to thatof voltage source 312 is applied to the gates of transistors 304 and 305turning them off while a much higher voltage (about zero volts)sufficient to turn on transistors 303 and 306 is applied to the gates ofthese last two transistors. Accordingly, transistors 303 and 306 providelow resistance paths for signals to travel from their drains to othersources. Transistor 306 is connected to one input lead of operationalamplifier 307. The other input lead to amplifier 307 is grounded througha filter comprising capacitor 307a and resistor 307b. Transistor 303 isconnected to shunt to ground the unused +TEMP signal source.

When transistor 318 is off, transistor 306 is on and the input voltagegenerated by the TEMP input transducer is applied to integratingamplifier 307. The input current to amplifier 307 is integrated bycapacitor 307f. Resistors 307i, 307 and 307h provide an additional meansfor controlling the time necessary for the voltage across capacitor 307fto reach a desired value. Zener diodes 307k and 307n limit the outputvoltage of amplifier 307 to within the input voltage limits ofcomparators 308 and 309. In normal operation diodes 307k and 307n arenot needed.

Thus, initially the output voltage from amplifier 307 has a linearlyincreasing positive shape. This output signal is passed to the positiveand negative input leads to comparators 308 and 309 respectively. Inputleads 308a and 30% to comparators 308 and 309 receive voltagesrepresenting manifold absolute pressure (the V,,,,,,, input 308b) andacceleration (the ATI-l, for change in throttle linkage position, input309g) respectively. These two leads are also coupled by capacitors 308aand 309a to ground. In addition, input lead 309h is coupled throughvariable resistor 30% and resistor 3091) to positive voltage source3101; and also through resistors 309d, 309f and 30% to negative voltagesource 312. The sliding contact on resistor 309a sets the thresholdvoltage for comparator 309.

Comparator 309 produces a low-level output signal in response to apositive-going ramp signal on lead 309j going more positive than thevoltage at the wiper of potentiometer 309C. This low-level output signalis applied to one input lead to NOR gate 315. For reasons to beexplained shortly, NOR gate 315 thus produces a high-level signal.

NOR gates 314 and 315 are connected as an RS flipflop. When the outputsignal from amplifier 307 is below the level of the reference signal onlead 309k, comparator 309 produces a high-level output signal. It shouldbe noted that the reference signal on lead 30% to comparator 309 alwayshas a higher value than does the reference signal from source 3081:which is transmitted on lead 308C to comparator 308. (Le, V V309 Thusthe output signal from NOR gate 315 is low-level. This low-level signalis transmitted through resistor 316 to the base of PNP transistor 317thereby turning on transistor 317. As described above, the collectorvoltage of transistor 317 maintains conducting the channels associatedwith FET transistors 303 and 306. When, however, as described above, thepositivegoing ramp signal from amplifier 307 reaches a selected value (Vthe output signal from comparator 309 drops to low-level therebyswitching the output signal from NOR gate 315 from low-level tohigh-level. This high-level output signal turns off transistor 317 andis fed back to the other input of NOR gate 314. NOR gate 314 produces alow-level signal which is applied to the base of transistor 318 throughresistor 319. This low-level signal turns on transistor 318 therebyraising the voltage on the gates of the FET transistors 304 and 305 tozero. Consequently, these two transistors turn on while transistor 317shuts off dropping the gate voltages of, and thus turning off, FETtransistors 303 and 306. The +TEMP signal from the temperaturetransducer is now applied through resistor 301 to the input lead ofoperational amplifier 307. The charge previously built up on capacitor307fnow is dissipated. Accordingly, the level of the output signal fromoperational amplifier 307 drops. When this output signal drops beneaththe level of the signal V from source 30% on lead 308c to comparator308, the output signal from comparator 308 drops to a low level. Thisturns off transistor 318 and turns on again transistor 317.

Thus the output signal from amplifier 307 assumes a triangular shape, asshown in FIG. 2. The period of the waveform varies with the rate atwhich capacitor 307f charges and discharges. The higher the charge rateor current, the shorter the period. The current, in turn, is directlyproportional to the voltage difference between the +TEMP and TEMP inputleads. As the potential difference between the signals on lead 308C tocomparator 308 and lead 309k to comparator 309 increases, the amplitudeof the periodic triangular shaped wave of amplifier 307 increases andthus the period of this wave increases. This results in a longerinjection time. Conversely, as the potential difference between thesignals on these two leads decreases, the injection time decreases. Thepotential on lead 3086 is controlled mainly by manifold absolutepressure. (See FIG. 4b, amplifier 430). In addition, engine speed alsoinfluences the particular signal level on lead 3080.

The voltage ATH from source 309g which controls the voltage on lead30911 to comparator 309 is primarily controlled by the output signalfrom the circuit shown in FIG. 8 which represents the position of thethrottle and the rate of change of position of the throttle.

It should be noted that the triangular signal from operational amplifier307 makes it possible to easily service the system by merely looking atthe slope and amplitude of the output signal from operational amplifier307. The amplitude of this output signal is primarily controlled by themanifold absolute pressure and secondarily by engine crankshaftfrequency. The slope of this trangular waveform, on the other hand, iscontrolled primarily by input temperatures and secondarily by transientoperating conditions such as wide-open throttle. Thus, errors in theinjection period can be attributed to either an incorrect amplitude ofthe output signal from operational amplifier 307 or, an incorrect slopeon this output signal. This feature thus allows the system to beanalysed when the injection period is incorrect to determine whether ornot the error arises because the output signal from amplifier 307 has animproper amplitude, in which case the error is in the manifold absolutepressure section of the system, or from an improper slope, in which casethe error is in the temperature sensing portion of the system.

Any particular component in the system can easily be replaced by acomponent known to be functioning correctly and the influence of thiscomponent on the output signal determined. If there is no change in theshape of this signal, then the component replaced is known to befunctioning properly and the search for the improperly functioningcomponent continues until this component is found.

When the error is not in the external transducers, but rather in theprocessing circuitry itself, analysis of the trianguluar output signalfrom amplifier 307 for known values of all the input parameters whichaffect this signal enables one to determine the particular section ofthe processing circuitry which is malfunctioning.

The RS flip-flop comprising gates 314 and 315 produces a square wavefrom the output lead of NAND gate 314a as shown. If desired, an outputsignal can also be taken from the output lead of NOR gate 315 or fromnumerous other places in the circuit. The output signal from oscillator30 is, as described above, used to drive pulse groups through delay 20(FIG. 1).

FIG. 3 shows the circuitry for detecting, and operating on, signals fromtransducers connected to the throttle linkage, the engine startercontrol circuit, the water temperature and the air temperature. First,the operation of the circuitry connected to the wide open throttletransducer will be described. The throttle is fully depressed only whenthe driver accelerates at a maximum rate. Maximum acceleration requiresmore fuel than does normal acceleration. In this condition, a cam,electronic sensor, or other means actuated by the throttle linkagegrounds or brings to a low-level the lead in FIG. 3 labeled WOT therebyshutting off transistor 331. (Diodes 331a and 33112, connected to thebase of transistor 33], reduce the probability of noise affecting thestate of transistor 331. These diodes can be omitted, if desired.) Thecollector voltage on transistor 33] is thus driven to the high levelrepresented by the positive voltage source V This turns on transistor332. The collector voltage on transistor 332 then drops to a low level,thus lowering the input voltage to operational amplifier 338. This inputvoltage is applied to operational amplifier 338 through a filtercomprising resistor 338 a and capacitor 337. Capacitor 337 smooths thetransition from wide-open throttle to steady state operating conditions.As is well known, the output voltage V from an operational amplifier isrelated to the input voltage V, by the approximate equation 5 -Vi(RI/R2) (n which can be rewritten with respect to amplifier 338 as Inequation l R is the feedback resistor and R is the input resistorthrough which the input signal passes to the input lead. Usually anoperational amplifier has high gain so the nongrounded input lead of theopera tional amplifier can be treated as a virtual ground.

The output signal from operational amplifier 338 is next transmitted toa resistive network comprising resistors 3400, 342, 340b, 340d and 340a.Resistors 340b and 342 are negative temperature coefficient thermistors,the resistances of which decrease as the engines water temperatureincreases. This network essentially serves as the input resistor (R inequation (1)) between the input signal and the input lead to operationalamplifier 340. Feedback resistor 340f is equivalent to resistor R inequation (I). The circles labelled 340i, 340 and 340k denote connectorsby which external transducers are connected to the processing circuitry.This processing circuitry typically is an integrated circuit. As theresistances of resistors 342 and 34% decrease, the output voltage fromoperational amplifier 340 increases. As explained above in conjunctionwith equation (I this increases the difference between the voltage onthe leads labeled +TEMP and 'TEMP (FIGS. 2 and 3) and decreases theperiod of the output signal from oscillator 30 (FIGS. 1 and 2).

Operational amplifier 341, together with input resistors 341e, 34l f,feedback diode 341c and capacitor 341b, output resistor 3413 and diode3410 is a feedback circuit which prevents the output signal ofoperational amplifier 340 from becoming greater than that at unity gain.This feedback circuit comes into operation when the resistance ofthermistors 34011 and 342 drops below the value associated with unitygain for operational amplifier 340. This entire feedback circuit is inparallel with feedback resistor 340f.

Diodes 341a and 341c associated with operational amplifier 341 doseveral things. Diode 341a insures that the output signal of operationalamplifier 341 as seen by the input of operational amplifier 340 is ofone polarity only. Diode 34lc limits unwanted excursions of operationalamplifier 341. Capacitor 341b, connected in parallel with diode 341e,insures gain and phase compensation of operational amplifier 340 and 341to prevent circuit oscillation.

The next stage of the circuit comprises another operational amplifierstage with feedback very similar to the just described operationalamplifier stage. Operational amplifier 344 has an input resistivenetwork comprising resistors 344a, 344b (both thermistors which measureair temperature) and resistors 3444' and 344d. Capacitor 344g filtersout unwanted noise. Resistors 344k and variable resistor 3441' areconnected in the feedback path of operational amplifier 344. Resistor344i provides stage gain adjustment. These resistors are equivalent toresistor R in equation (I). Operational amplifier 345 and associatedcircuitry provides a feedback path to control the output signal fromoperational amplifier 344 in the same manner as described above inconjunction with operational amplifiers 340 and 341. Amplifier 345 andits associated circuitry can be omitted, if desired, depending upon thespecified system response to input temperature and the absolute valuesof the thermistors chosen for resistors 344a and 344b. For example, whenthe control system is used over a wide temperature range, operationalamplifier 345 might be omitted.

The output signal from operational amplifier 344 represents theinfluence of air temperature on the period of oscillator (FIGS. 1 and2). It should be noted from equation l that the output signal V fromamplifier 344 is related to the input signal V to amplifier 340 asfollows (provided that the feedback circuits which include amplifiers341 and 345 are inactive):

Resistors R1 and R2 with the appropriate subscripts represent thecombined resistances connected in the feedback circuits and inputscircuits of the correspondingly numbered operational amplifiers,respectively. From equation (3) it is apparent that the output signalV0344 represents the multiplicative effect of temperature changesreflected in the values of R and R When starting a cold engine, morefuel is required than for normal operating conditions at the sametemperature. Thus, in FIG. 3, a crank motor transducer produces apositive output signal on lead 355 upon the application of a voltage tothe starter motor. This signal turns on transistor 333. Transistor 333thus lowers the output voltage applied to one input lead of operationalamplifier 338. Capacitor 337 stores a charge reflecting a new inputvoltage to operational amplifier 338. (It should be mentioned thatcapacitor 337 performs in the same way whether the voltage drop acrossresistor 334 is generated by a wide open throttle signal or a crankmotor signal.) The time during which extra fuel is injected into theengine after the removal of the crank signal is determined by the valuesof resistors 334 and 338a and capacitor 337. The charge stored oncapacitor 337 depends on the voltage drop across resistor 334. Whenvoltage is no longer applied to the starter motor, the charge oncapacitor 337 prevents the circuit from immediately shutting off extragas applied to the engine. But, as the charge on this capacitor returnsto normal, the period of oscillator 30 and thus the fuel supplied to theinjectors gradually returns to the normal value dictated by the otherengine operating conditions. The size of capacitor 337 is varied toreflect the different engines or vehicles used with the electroniccontrol system of this invention. As the size of the en gine increases,the engine takes longer to respond to changes in demand and capacitor337 is made larger. Also, as vehicle size increases. capacitor 337 ismade larger because more fuel is required to accelerate the vehicle.

If a driver accelerates using wide open throttle, but then suddenlytakes his foot off the accelerator, another circuit to be describedlater shuts off all fuel to the engine. Meanwhile, the charge oncapacitor 337 returns to normal. The result is that minimal excesshydrocarbons and carbon monoxide in the form of incompletely burned fuelare expelled into the environment. For a large engine, the time constantof the RC circuit of which capacitor 337 is a part is approximately oneto two seconds.

Operational amplifier 338 should have a low output impedance to reducethe errors contributed by this impedance to the signal produced bythermistor 34019. Likewise the output impedance of operational amplifier340 should be low to similarly minimize the impact of this impedance onthe following temperature sensing III thermistors. Output resistances ofoperational amplifiers are typically less than 10 ohms. Thermistors, bycomparison, have an impedance from several hundred ohms to severalthousand ohms.

Thermistors have been described in FIG. 3 for sensing water temperatureand air temperature. An additional operational amplifier stage can beadded, if desired, for fuel temperature. Other operational amplifierscan be added with gain-controlling thermistors to sense any othertemperatures of importance in controlling the fuel demanded by theengine. Among these temperatures are exhaust gas temperature, oiltemperature, block temperature, and in more sophisticated sys tems,individual cylinder temperatures.

PROCESSOR l0; CONTROL OF INJECTION TIMING AND SYNCHRONIZATION Processor10 processes the signals from the and 720 transducers.

FIGS. 5a and 5b show in more detail the amplification circuits used withthe 90 transducer and the 720 transducer. The operation of thesetransducers will be described in conjunction with the 90 pickupcircuitry. The circuitry associated with the 720 pickup works insubstantially the same manner, only less frequently. A signal from the90 transducer. which can be mounted on the distributor shaft,crankshaft, or camshaft, is de tected and transmitted directly on leads501 and 502 to difference amplifier 507. The output signal fromamplifier 507 is connected to one input lead of AND gate 511 and isfiltered by capacitor 509. The other input lead to this AND gate isconnected to a positive voltage source. The output signal on lead 513from AND gate 511 changes from a low level to a high level in responseto a pulse detected by the 90 pickup transducer. The differential modeconnection from the 90 transducer to difference amplifier 507 preventscommon mode signals and stray signals from activating AND gate 511.

The 720 signal is processed in a similar manner using the circuit ofFIG. 5a.

The output signal from the 90 pickup circuitry on lead 513 is sent totransient processor 50 (FIG. I), which will be described later.Processor 50 provides special corrections for certain types ofoperations. The output signal from the 720 pickup circuitry is sent toprocessor 10 only.

It should be noted that all degrees used in this specifi cation aredegrees of rotation of the crankshaft. In a four-cycle, eight-cylinderengine, a fuelair mixture is inducted into a new cylinder every 90rotation of the crankshaft. For all types of four-cycle engines, anengine cycle is completed every 720 rotation of the crankshaft.

FIG. 5c shows in more detail the logic circuitry of processor 10 anddigital delay 20. The output signal from processor 10 (FIG. 1) comprisestwo pulses when this output signal is generated by a signal from a 90pickup transducer. However, when an input signal is received from the720 pickup transducer, processor 10 produces a four pulse output signal.

The two pulse output signal occupies two locations in digital delay 20while the four pulse output signal from processor 10 occupies fourlocations of digital delay 20. The 90 pickup signal is inverted inamplifier 523 (FIG. 5c) and then sent to 90 memory 525. Memories 52S and526 may typically comprise JK (or D) flipflops Fairchild device type9L24 as manufactured by the assignee of the present application. There,the 90 signal is held for a period of time sufficient to place twopulses in shift register 530-1, the first register in digital delay line20. The digital delay line 20 comprises shift registers 530-1, 530-2530-N, and 531; which shift registers may typically comprise 8-bit shiftregisters Fairchild device type 93L28 as manufactured by the assignee ofthe present application. The presence of pulses in the first twolocations in shift register 530-! is detected by NAND gate 527. Thesignal on the input lead to NAND gate 527 from 720 memory 526 isnormally high level. The signals on the two input leads to NAND gate 527from shift register 530-1 are normally low level. Thus NAND gate 527produces a normally high-level output signal. However, upon the transferof the two high-level pulses from memory 525 to the first two locationsof shift register 530-1, the signal levels on all three input leads toNAND gate 527 will go high and the output signal from NAND gate 527 willgo to a low level. This produces a high-level output signal from NORgate 528 which in turn is transmitted through inverter 529 to the resetterminal of 90 memory 525 to clear this memory. Thus, the output signalfrom 90 memory 525 drops to a low level again. Consequently, theremaining clock pulses from oscillator 30 place low-level signals in thefirst location of shift register 530-1 rather than a high-level signal.Meanwhile, the high-level pulses formerly in this location are shiftedthrough delay line 20.

The signal on the output lead from 720 memory 526 is normally highlevel. When, however, the 720 pickup signal is received, the outputsignal from 720 memory 526 drops to a low level thereby disabling NANDgate 527. However, when shift register 530-] contains four pulses in itsfour locations, NAND gate 534 is activated and produces a low-leveloutput signal. This low-level output signal is transmitted through NORgate 528 and inverter 529 and again changes the output signal from 90memory 525 from high level to low level.

The 720 memory 526 is deliberately activated slightly earlier than the90 memory 525 and thus disables NAND gate 527 before memory 525 isactivated. Thus, the 90 memory will have a high level output signalstored in it for four periods of the signal from oscillator 30 duringwhich time the output signal from 720 memory 526 is low level(activated). The output pulse from inverter 529 also clears 720 memory526.

The presence of two pulses in shift register 530-] denoting the receiptof a signal from the 90 transducer by processor 10 results in NAND gate535 producing a low-level output pulse. NAND gates 534 and 535 comprisedata decode 100 (FIG. I). The low-level output pulse from gate 535 issent to A" counter 90 (FIG. 1). Counter 90 controls, through injectordecode 80, the particular fuel injector through which fuel is to beinjected and initiates fuel injection by a change in its state inresponse to the signal from data decode 100. Injector decode 80 selectsin sequence the injectors to be activated in accordance with the firingor injection order of the engine. The first injector to be activated isopened for a time determined by the time necessary for the two pulses indigital delay to pass from the first shift register 5150-] (FIG. 5c) indelay line 20 to the last shift register 531 in this delay line. NANDgates 532 and 533 comprise data decode 60 (FIG. 1). When the two pulsesfrom a 90 pick-up transducer reach shift register 531, a signal is sentfrom NAND gate 533,

which detects the presence of these two pulses in the first twolocations in shift register 53], on lead 539 to B counter (FIG. 1).Counter 70 then sends a signal to injector decode to shut the injectorvalve. Each signal from 8" counter 70 to injector decode 80 is routed tothe correct injector valve, as is each signal from A counter 90, by thelogic matrix within injector decode 80. It should be mentioned thatinjector decode 80 can be a standard demultiplexing circuit.

As explained above, the frequency of the output signal from computingoscillator 30, and thus the period of this signal, vary in response tothe input signals to controlling oscillator 30. Digital delay line 20has a fixed number of stages M where M X N. X is the number of extrastages in delay line 20 required to detect the presence of pulse groupsat the beginning and end of delay line 20. In this case, X is four (4).The real time period required for a signal to pass through delay 20, isthat elapsed time period needed for the computing oscillator togenerator N pulses. This elapsed time defines the period that acurrently active injector will be held open. Accordingly, the times forwhich the injector valves are left open as the result of control signalsfrom injector decode matrix 80 vary smoothly with variations in thefrequency of the output signal from oscillator 20. The output signalfrom the oscillator is updated N times while an injector valve is open.Because the time that an injector is open is the integral over time ofthe period of the output signal from oscillator 30, noise tends to havelittle effect on the resultant injection timev The frequency in cyclesper second of the output signal from oscillator 30 is typically greaterthan 2/5 times the engine RPM.

It should be noted that the pulses present in memory 525 and 720 memory526 (FIG. 5c) are invariably removed or erased prior to the removal ofthe 90 or 720 pick-up signals on leads 521 and 522 respectively andcertainly long before the valve gear train rotates 90.

Upon activation of the 720 transducer, four pulses are injected insequence into delay line 20. The receipt of the second of the four highlevel pulses in shift register 531 activates NAND gate 533 which steps Bcounter 70 to denote the injector then open. This activates injectordecode 80 to close this injector.

The receipt of the fourth high level pulse in shift register 531 (FIG.50) activates NAND gate 532. NAND gate 532, which produces a normallyhigh level output signal, now sends a low level signal to 8" counter 70(FIG. 1) to clear this counter. The output signal from NAND gate 534(FIG. 5c) is similarly sent to A counter 90 (FIG. 1) to clear thiscounter once each engine cycle. Thus NAND gates 534 and 532 synchronizethe system once each engine cycle.

Both the A" counter 90 and the B" counter 70 are essentially binaryregisters which can store pulses representing P digital numbersrepresenting the numbers of the cylinders into which fuel is to beinjected. In an eight cylinder engine, counters 70 and 90 can storepulses representing digital numbers from 0 to 7. By the use of feedbackwith a three bit counter, one can restrict the maximum count stored inthe counter to six and thus convert the counter to use with six cylinderengines. The number stored in A counter 90 represents the cylinder whichis to receive the fuel which is being, or has been injected. Setting thecount in A counter 90 to zero in response to a change in state of the720 pickup signal means that the injector corresponding to a zero in Acounter 90 has been opened. Setting B counter 70 to zero in response tothe delayed 720 pick-up signal reaching shift register 531 means thatthe injector corresponding to zero count will be closed.

COUNTERS 70 AND 90 AND INJECTOR DECODE 80 FIG. 6 shows the manner inwhich the signals from NAND gates 534 and 535 (FIG. c) are used tocontrol the state of A counter 90 (FIG. 1). Counter 90, shown in FIG. 6,comprises one-shot 605 and counter 608. Counter 608 may typicallycomprise a 4-bit binary counter Fairchild device type 93L16 asmanufactured by the assignee of the present application. Signalsdenoting fully closed throttle position (denoted PCT) and flooding ofthe engine are transmitted through NOR gate 603 to one input lead of ANDgate 604. Open clock pulses from NAND gate 535 (part of Data Decode 100.FlGS. 1 and 5c) are transmitted to the other input lead of AND gate 604.As will be explained shortly, signals from one-shot 605 in response tothe FCT or flood conditions prevent additional fuel from being injectedinto each cylinder. AND gate 604 acti vates one-shot 605. The period ofone-shot 605 is controlled by the values of resistor 60511 and capacitor605a connected to one shot 605 and the positive voltage source as shown.The other input lead to AND gate 604 is connected by lead 601 to theoutput lead from NAND gate 535 (FIG. 5c). NAND gate 535 produces anoutput pulse every time the 90 pickup transducer produces a pulse. Thepulse from gate 535 triggers oneshot 605 and also is transmitteddirectly to counter 605 where it changes the count by one unit.Periodically, an output pulse is produced by NAND gate 534 indicatingthe receipt of a signal from the 720 transducer. This output pulse istransmitted on lead 602 directly to counter 608 and there resets counter608 to zero. The count in counter 608 controls the states of the outputsignals on lead 609a through 609m from opening de code 609. Openingdecoder 609 may typically comprise a one-of-ten decoder Fairchilcldevice type 93101 as manufactured by the assignee of the presentapplication. In one embodiment counter 608 can store up to a three (3)bit binary code word. Other embodiments of counter 608 can store n-bitbinary code words, where n is a selected integer. When counter 608 thusreceives a pulse, the signal on the output lead from opening decode 609corresponding to the new binary code word stored in counter 608 goes toa low level. This low-level signal has a duration controlled by theoutput pulse from one-shot 605. One-shot 605 was triggered by the samepulse from NAND gate 535 that changed the state of counter 608.

When the system is in synchronization, the count in counter 608 will goto zero just prior to the receipt of the 720 reset pulse. From thedescription of the cir' cuitry of FIG. 50, it should be remembered thatthe 720 reset pulse comes from NAND gate 534 two clock periods laterthan does the 90 pulse signal from NAND gate 535. Thus, if the system isin synchronization, open counter 608 will already have been set to zeroand the reset pulse from NAND gate 534 (which detects the 720 transducersignal) will arrive after the 90 transducer pulse has advanced thecounter 608 to zero. Thus when counter 608 is synchronized with the restof the system, there is no change in the state of this counter upon thereceipt on lead 602 of the output signal from NAND gate 534 (FIG. 5b).

If, however, counter 608 is out of synchronization, the reset pulse from720 decoder NAND gate 534 would reset counter 608 to zero. The error ininjection time of the first cylinder in the injection sequence resulting from this lack of synchronization is the two clock-pulse delaynecessary to generate the 720 signal. Because of valve inertia, theinjector will not have opened significantly in that time. By increasingthe length of the delay line, or the clock frequency, or both, thiserror can be reduced. Lack of synchronization can possibly also causeexcessive fuel in some cylinders and not enough fuel in other cylinders.

FIG. 6 also shows closing decoder 611 which closes the injectors.Closing decoder 611 may also typically comprise a one-of-ten decoderFairchild device type 93L0l. The closing clock signal is transmitted toclose counter 610, part of B counter (FIG. 1), from one of two sources;NAND gate 533 produces an output pulse when the pickup pulse grouptransmitted into delay line 20 reaches shift register 531. Close counter610 may also typically comprise a 4-bit binary counter Fairchild devicetype 93L16. This pulse from NAND gate 533 is transmitted to closecounter 610 to change the count recorded in this counter. Upon thereceipt of the new count, the signals from close counter 610representing this new count are transmitted to closing decoder 611 whichactivates the proper output leads 611a through 611n to close theinjector corresponding to the cylinder represented by the new number incounter 610. Counter 610 is synchronized by a signal from NAND gate 532(FIG. 56).

The output signals from the opening decode circuit 609 are sent twoplaces. First, these signals are sent to the corresponding input lead ofcircuits 614 and 615. Circuits 614 and 615 each contain four flip-flopsand thus control eight injectors. Circuits 614 and 615 may each forexample, comprise a quad latch Fairchild de' vice type 931.14 asmanufactured by the assignee ofthe present application. A low levelsignal on output lead 609a is transmitted to the input lead to flip11opl of circuit 614, on the lead labeled 6090. This signal changes thestate of this flipflop. The signal on the output lead from flip-flop lin circuit 614 is transmitted through half adder 616a andbuffer-inverter 617a. The current from inverter 617a comprises alow-level holding current which holds open an injector until a signalfrom closing decoder 611 changes the state of the flip-flop. The outputsignal on lead 609a from opening decoder 609 simultaneously is sent tothe corresponding NOR gate 6130. This produces a high level signal onthe output lead from NOR gate 6130. This high level signal drives thesame injector valve hard open thereby increasing the speed with whichthe injector valve opens and thus the amount of fuel placed in thecylinder in a given time.

It should be noted that the time an injector is left open is determinedby the time it takes for the pulse groups to travel through digitaldelay line 20 (FIGS. 1 and 50). As engine speed increases, a pulse groupwhich opens a first injector can still be traveling through delay line20 when a second pulse group is injected into deiay line 20 by the nextsignal from the 90 transducer. In response to this second pulse groupentering the delay line, a second injector is opened while the firstinjector is still open. As the engine speed increases, up to seveninjectors can be open at the same time using the system of thisinvention. In theory, all eight injectors can be open at the same time.However, close counter 610 produces a closing signal for 90 ofcrankshaft rotation. Thus any and each injector must be closed forone-eighth of an engine cycle. Therefore, at any time during the enginecycle, one injector must be closed. The system, however, can be modifiedto avoid this limitation by having close counter 610 produce a closepulse of a more limited duration.

ln one'embodiment fuel injection preferably occurs a few degrees beforethe intake valve to the cylinder opens. Typically, the intake valve isopen for about 200 to 230 rotation of the crankshaft. On the other hand,the injectors are injecting fuel over from 10 to rotation of thecrankshaft at idle and up to 600 at full power. If the driver decides toaccelerate before the fuel being pulled into a cylinder has beenignited, the injector associated with that cylinder can be reopened toinject more fuel into the manifold and thus into the cylinder inresponse to the acceleration signal. This feature provides additionalflexibility for the operation of the system and is described next.

DOUBLE lNJECT DECODE 607, 612, 616 AND 618 FIG. 6 also shows doubleinjector decoder 612. The decoder 612 may also typically comprise aone-of-ten decoder Fairchild device type 93L01 as manufactured by theassignee of the present application. This decoder is provided to open apreviously opened and now closed injector in response to a signal fromtransient processor 50 (FIG. 1) that the driver has pressed down on theaccelerator.

Pressing down on the accelerator results in a highlevel signal beingtransmitted on lead 606 to one input lead of NAND gate 607 therebyenabling NAND gate 607. The generation of this pulse is to be describedin conjunction with FIG. 8. When the pulse from NAND gate 535 (FIG. 5c)is transmitted on lead 601 to AND gate 604 thereby activating one-shot605, the output signal from one-shot 605 goes to a high level. Thisoutput signal is applied to the other input lead of NAND gate 607. NANDgate 607 thereby puts out a low'level output signal which activatesdouble injector decode 612. Double injector decoder 612 works inthe sameway as open decoder 609 but is programed to open the injector associatedwith a cylinder for which fuel was previously injected so that anadditional amount of fuel can be injected for use by that cylinder.

It should also be noted that the acceleration signal on lead 606 istransmitted to the half-adders 616a through 616d and 6180 through 618a.These gates are activated either by a single signal from thecorresponding connected flip-flop in register 614 or 615 or by thesimultaneous presence of an acceleration signal on lead 606 togetherwith a signal on the next following flip-flop in the registers 614 or615. Thus the presence of a signal on acceleration lead 606 results in agiven flip-flop in registers 614 or 615 activing not only the half-adder616 or 618 connected to that flip-flop, but also the precedinghalf-adder connected to the flip-flop.

MANlFOLD PRESSURE SIGNAL PROCESSOR F IG. 4a through 4d show theelectronic circuitry used to generate signals representing manifoldpressure. As manifold pressure increases, the airflow through themanifold increases and thus the fuel required to be injected into eachcylinder increases. This means that the injection time must alsoincrease. An increased injection time requires a decrease in thefrequency of the output signal from computing oscillator 30 (FIG. 1).Accordingly, the output voltage VAMP from operational amplifier 430 (F1G. 4b), to comparator 308 (FIG. 2) must decrease algebraically. Thisoutput voltage changes the reference level on one input lead tocomparator 308, thus changing the time required for the output signalfrom operational amplifier 307 to change the state on the flip-flopcomprised of elements 314 and 315.

The signal representing manifold pressure is sent through resistor 4110to input lead 41 1h of operational amplifier 411. The voltage on inputlead 41 1h of operational amplifier 411 is held at virtual ground as ina standard operational amplifier with feedback. Diode 411d insures thatwhen the input voltage V drops beneath a selected reference voltageestablished by voltage source 412 and resistors 411a and 411b, theoutput voltage from the operational amplifier 421 will be clamped abovevirtual ground by the voltage drop of a forward-biased PN junction, Onthe other hand, as the input voltage V to operational amplifier 411climbs above the selected reference voltage, the output voltage from theoperational amplifier drops linearly at a rate controlled by the ratioof resistor 411g to resistor 411a. Diode 411d acts as an open circuit inthis circumstance while diode 411e becomes forward biased.

By varying the voltage represented by source 412 or either of resistors411a and 411b, the voltage V at which the characteristic curve of V,versus V assumes a negative slope is varied, as shown in FlG. 4d. FlG.4d shows several curves all with different values of V at which thebreakpoint in the curve of V, versus V, occurs. The curve which passesthrough the center of the graph has voltage source 412 equal zero. Whenvoltage source 412 is positive, the breakpoint in the characteristiccurve shifts to a negative value of V The slope of the non-horizontalportions of the curves in FIG. 4d is given by V /V, -R /R,. Reversal ofthe polarity of the diode as shown by the diode in dashed lines in FIG.4e results in a curve shown by the dashed lines in FIG. 4d. Thus theoutput signal from operational amplifier 411 with diodes connected asshown has a piece-wise linear characteristic.

Operational amplifier 421 operates in the same manner as doesoperational amplifier 411.

The reference voltage 412 connected to input lead 41 1h is selected tocorrespond to a selected low pressure, such as five inches of mercuryabsolute which in turn corresponds to a very low air flow rate to theengine. Thus, for manifold pressure beneath five inches of mercury, theinjection time is minimized to a selected value. 1n this condition, thetypical engine has a negative torque output. As the manifold pressureincreases, signifying a larger air flow to the engine, operationalamplifier 411 begins to produce an increasingly negative output voltage.This output voltage then is transmitted to multiplying circuit 414.Likewise, operational amplifier 421 produces an increasingly negativeoutput voltage as the manifold pressure increases above the pressureassociated with its reference voltage as set by resistors 421a, 4212 and42 1 f. The output signal from operational amplifier 421 is likewisesent through resistor 422 to multiplying circuit 424.

Circuits 414 and 424 are shown in more detail in FIG. 4f. The inputvoltage to the circuit is controlled by the settings of potentionmeterresistors 440C and 4404. The output voltages from the operationalamplifiers are brought into circuits 414 and 424 on leads 9.

An additional signal is brought into each of multiplying circuits 414and 424 on lead 4. These signals are derived from operational amplifiers407 and 408 (FIG. 4a) which in turn operate on signals from operationalamplifiers 403, 404 and 405 (FIG. 4a). These last three amplifiersoperate in the same manner as operational amplifiers 411 and 421 exceptthat the diodes in the feedback circuits of amplifiers 403, 404 and 405are reversed in polarity. The polarities of the diodes associated witheach operational amplifier in FIG. 4a are determined by the shape of thetransfer function desired for the circuit. Thus the transfercharacteristics of these operational amplifiers correspond to the dashcurve shown in FIG. 4d with the break-point in the characteristic ofeach amplifier being controlled as described above.

The input signal to operational amplifiers 403, 404 and 405 areproportional to engine freuency. These signals can be generated from afrequency signal obtained from the crank shaft or the distributor or anyother rotating part of the engine suitable for such a measurement. FIG.7 shows circuitry suitable for generating these signals.

The output signals from operational amplifiers 403 and 404 are fed tothe input lead of operational amplifier 408. The output signal from thisoperational amplifier is denoted S1 and is the input signal on lead 4140of multiplier 414 (FIG. 4b). FIG. 4hshows a typical transfer function ofSI versus engine frequency.

Likewise, the output signal from operational amplifier 405 is passedthrough operational amplifier 407 and then is sent on the lead denotedS2 to lead 424a of multiplier 424 as shown in FIG. 4b. FIG. 43 shows atypical transfer function of S21 versus engine frequency. Note that thetransfer function of FIG. 43 has only one breakpoint because only oneactive diode circuit (the circuit associated with amplifier 405) is usedto generate the curve of FIG. 43. The transfer function of FIG. 4f hastwo such breakpoints because two such circuits (the circuits associatedwith ampliiers 403 and 404) are used to generate the curve of FIG. 4f.

Each multiplier comprises a well-known commercially available circuitsuch as the 4A 795, made by Fairchild Camera and Instrument Corporation.Each multiplier takes two input signals on leads 4 and 9 and produces anoutput signal on lead 14 proportional to the product of these two inputsignals. The way in which these multipliers work is well known and thusthese multipliers will not be described in detail.

The output signals from multipliers 414 and 424 (FIG. 4b) aretransmitted through input resistors 414b, 4l4c and 4241;, 424c to theinput leads of operational amplifiers 415 and 425 respectively. Theoutput signals from operational amplifiers 415 and 425 are thentransmitted to one input lead of operational amplifier 430 through inputscaling resistors 415C and 425C. The resulting voltage V fromoperational amplifier 430 is sent to input lead 308b (FIG. 2).

FIG. 4c is a curve of injection time versus the ratio of manifoldabsolute pressure to atmosphere pressure. As injection time increases,the period of the signal from oscillator 30 (FIG. 1) must increase andthus V 1, must decrease algebraically. Note that the slope of the outputsignal from operational amplifier 307 is the amplitude of Vmp.

It should be noted that the number of discontinuities in the curve ofFIG. 4c can be controlled by controlling the number of operationalamplifiers used to generate this curve.

TRANSIENT PROCESSOR 50 FIG. 7 shows the circuitry used to control thecutoff of fuel to the engine. Pulses from the tachometer transducer(located on the crankshaft, for example) are sent on lead 700a toone-shot 701. One-shot 701 produces an output pulse of about 3milliseconds duration. Operational amplifier 703 has a feedback networkcomprising a parallel-connected capacitor 703d and resistor 703C and aninput resistor 703a. This configuration results in operational amplifier703 producing an output voltage proportional to the frequency of thepulses from one-shot 701. In one embodiment, amplifier 703 was set toproduce 1 volt per 1,000 rpm of the engine.

The output signal from operational amplifier 703 is sent throughresistors 705a and Sfto the ungrounded input leads of comparators 706and 707 respectively. Output lead 70012 connected at node 700e to theoutput lead from amplifier 703 carries the signal from amplifier 703 toinput lead 4032' to operational amplifier 403 (FIG. 4a). The outputsignal from amplifier 703 is always negative in this embodiment.

An input voltage derived from a temperature transducer (which mightmeasure engine coolant temperature, for example) is transmitted toamplifier 704 on lead 700C. The output signal from amplifier 704, whichprovides a correction signal to compensate for deviations in the enginetemperature from its normal operating temperature, is sent to thenon-grounded input leads of comparators 706 and 707 through resistors705C and 705d, respectively.

The system has structure for preventing the engine from dying after thefully closed throttle position is sensed. The fully closed throttleposition is sensed by a transducer on the throttle linkage. An outputsignal denoting fully closed throttle is sent on lead 700d to JKflip-flop 708. The output signal from flip-flop 708 then stops theinjection of fuel. When the engine slows to a selected speed a givenamount above the speed at which the engine will die, fuel is resuppliedto the engine. An enabling signal, sent to flip-flop 708 from comparator707, insures that fuel is not shut off unless the engine speed issufficiently above the cut-off speed of the engine to insure that thereis some hysteresis in the engines fuel control function.

The signal to disable one-shot 605 (FIG. 6) is transmitted from theoutput lead on flip-flop 708 through NOR gate 709 to NOR gate 603 (FIG.6). Normally, the output signal from NOR gate 709 is low level. Thelow-level output signal from flip-flop 708 corresponding to a suddendeceleration or removal of the foot from the accelerator, results in ahigh-level output signal being produced on the output lead, of NOR gate709. This high-level signal disables one-shot 605.

In addition, a high-level output signal can be produced on the outputlead of NOR gate 709 by turning on transistor 710. This transistor isturned on in re sponse to a high-level signal on its base from the crankmotor transducer indicating that power is being applied to the crankmotor simultaneously with a low-level signal on its collector from thelead labeled WOT denot-

1. An electronic control system for a fuel injection system for use withan engine producing repetitive signals for synchronizing the injectionof fuel with the fuel requirements of said engine, which control systemcomprises: a. means for sensing the values of a plurality of parameterswhich determine the amount of fuel to be injected into utilization meansof said engine, and for producing a plurality of first signalsrepresenting these values; b. means, responsive to said first signals,for producing a second signal representing the injection time necessaryto inject the required amount of fuel into said utilization means; c.means for generating timing signals from the repetitive signals; d.delay means for receiving said timing signals, said timing signals beingshifted through said delay means at a rate determined by said secondsignal; and, e. means, responsive to the time necessary for said timingsignals to be shifted through said delay means, for controlling theopening and closing of fuel injection means disposed for injecting fuelinto said utilization means comprising:
 1. means for detecting thepresence of said timing signals in said delay line and for producing astart signal in Response to said timing signals; first means, responsiveto a signal from said means for detecting, for counting the number oftiming signals placed in said delay line and for controlling an injectordecode selector matrix in response to each timing signal placed in saiddelay means;
 3. an injector decode selector matrix means, responsive tosaid first means for counting, for selecting a particular fuel injectormeans the opening and closing times of which are to be controlled by acorresponding timing signal travelling through the delay line; and, 4.second means for detecting and counting the timing signals arriving atthe end of said delay means and for producing a signal in response tothe arrival of each timing signal to control, through said injectordecode selector matrix means, the closing of the fuel injector meansopened by said timing signal.
 2. A system as in claim 1 wherein saidutilization means comprises an engine containing P cylinders, where P isan integer representing the number of cylinders in the engine. 3.Structure as in claim 1 wherein said means responsive to said firstsignals, producing said second signal, comprise a plurality of amplifiermeans the gains of which vary according to the values of saidparameters, the output signals from said amplifier means comprising saidplurality of first signals.
 3. an injector decode selector matrix means,responsive to said first means for counting, for selecting a particularfuel injector means the opening and closing times of which are to becontrolled by a corresponding timing signal travelling through the delayline; and,
 4. Structure as in claim 1 including means for reopening inresponse to an acceleration signal, at least one previously closed fuelinjector means for the injection of additional fuel into the cylinderadjacent said previously opened fuel injector means.
 4. second means fordetecting and counting the timing signals arriving at the end of saiddelay means and for producing a signal in response to the arrival ofeach timing signal to control, through said injector decode selectormatrix means, the closing of the fuel injector means opened by saidtiming signal.
 5. Structure as in claim 1 including means for generatinga resynchronization signal to reset said first means for counting andsaid second means for detecting and counting to an initial state insynchronization with the operating conditions of said engine. 6.Structure as in claim 5 wherein said resynchronization signal isgenerated once every engine combustion cycle.
 7. Structure as in claim 1including: means for producing a cut-off signal in response to a suddendecrease in demand for fuel, said cut-off signal disabling said injectordecode selector matrix thereby to prevent additional fuel from beinginjected into said engine for the duration of said cut-off signal. 8.Structure as in claim 1 including: means for detecting traces ofundesired gases in the exhaust from said engine and for controlling theamount of fuel injected into said engine so as to reduce the amounts ofsaid undesired gases.